1. Field of the Invention
The invention relates to a rotary loop taker and, more specifically, to a rotary loop taker with a replaceable portion carrying upon it a portion of a raceway and a loop seizing tip. The replaceable portion must be stabilized in order to endure the severe impact of needle deflection. The present invention provides a means to stabilize the replaceable portion.
2. Background Art
A rotary loop taker is a device that must be incorporated into all lock stitch sewing machines. Perhaps 60% of the worldwide stock of sewing machines is of the lock stitch type. The rotary loop taker of the conventional type is precision machined to tight tolerances and is highly polished. These parts are costly items that often are short lived in today's industrial sewing environment.
The concept of using a replaceable tip rotary loop taker involves isolating the short-lived wear portions of the loop taker from the whole and making those portions removable, thereby saving that portion that is still undamaged and functional.
Much of the prior art relating to replaceable tip hooks shows rotary hooks having a vertically laminated construction. Rotary loop takers of this type unavoidably show cracks in which the thread can get caught. In addition, vertically laminated rotary loop takers are inherently relatively weak because they are not of a solid mass. Despite the disadvantages, the approach of vertical lamination has been followed at least since Dickson, U.S. Pat. No. 1,431,380, dated Oct. 10, 1922, with the exception of Badillo U.S. Pat. No. 4,493,278 and Grabowski U.S. Pat. No. 3,139,050, dated 6/1964.
Over ten years ago, Badillo, the inventor of the present invention, attempted to commercialize a replaceable tip hook, as shown in U.S. Pat. No. 4,493,278, dated Jan. 15, 1985. Although some promise was shown with that invention, the product ultimately was withdrawn from the market due to a malfunctioning mounting means and poor consistency of alignment between the parts that resulted in poor interchangeability of replaceable tips. The tolerances required to fit a replaceable tip upon the annular ting, as designed, made it impractical to meet a commercially viable price point. Badillo's attempt at allowing "play" or adjustability between the interchangeable parts, to meet these costs concerns, resulted in parts that could not withstand the extreme impact forces of the colliding needle into the replaceable tip free end. A needle strike against the replaceable tip would eventually move the tip relative to the annular frame and the needle eye out of alignment, and render the machine unuseable. The tip would have to be reset and proper timing reestablished to make the machine sew. The ensuing downtime to the operator caused by the constant need to re-time the machine and reset the tip caused the part to be withdrawn from the market.
Several patents have been granted in the art relating to replaceable tip hooks, but none known to the inventor herein has addressed the problem of consistency of fit and cost in the same manner as does the present invention. Indeed, much of the basic structure in Badillo's prior invention is incorporated into the present invention. In spite of having much of the same basic structure as applicant's prior invention in U.S. Pat. No. 4,493,278, the present invention differs in a novel and unobvious way. Applicant has now discovered a method in which a replaceable tip can be reliably manufactured in a cost effective way, and fit upon the annular frame without unwanted adjustability or "play".
Grabowsld, U.S. Pat. No. 3,139,050, departs from the vertical lamination approach of the prior art by having a solid, integrally formed loop seizing point with a downwardly extending lug, a curvature substantially corresponding to the annular frame, a tapered free end, and a rear end having a mounting hole for accepting a screw means. The lug nests within a notch formed upon the annular frame. However, his invention differs from the present invention in several important ways.
Grabowski has a first fixed protuberance that is located forward of the lug. Because his annular ring has no cutaway portion to facilitate thread exit off the loop seizing point, Grabowski utilizes the forward end of his loop seizing beak to form a mating cavity 61 to receive an axially fixed protuberance 54.
Grabowski has a second protuberance and mating cavity including a T-member 55 mating with a cavity 63. A pivoting movement is required to allow the loop seizing beak to be removed from the mating cavity. Grabowski's loop seizing beak can only nest within the mating cavity if a radially sliding motion is performed so that the lug can be pivoted therein. The complexity of the design of Grabowski's lug, T-member, and cavity may require very precise and expensive matching and tolerance control.
Dickson, U.S. Pat. No. 1,431,380, dated Oct. 10, 1992, shows a solid integrally formed loop seizing point with a downwardly extending lug to mount a notched section of the annular frame. However, with only one screw means to securely fasten the loop seizing point to the annular frame, the rotary loop taker of his invention would not appear to be able to endure the extreme impact required of the industrial sewing machines of today.
Despite great effort and volume of thought, to the knowledge of the inventor herein, a commercially viable replaceable tip rotary loop taker has yet to successfully appear on the market. The present invention teaches the elements of manufacturing a replaceable tip rotary loop taker with both the economical and functional requirements to fulfill this long and urgent need.